The present disclosure relates generally to the field of layers for magnetic recording media (e.g., hard disks, removable media, magnetoresistive memory, etc.). More particularly, the disclosure relates to layers for high anisotropy magnetic recording media including one or more exchange coupled granular layers.
As the grain size of layers in magnetic recording media is decreased in order to increase the areal density (e.g., to increase the capacity of the media without increasing the media size), a threshold known as the superparamagnetic limit is reached for a given material and temperature. The superparamagnetic limit is a physical constraint, beyond which stable data storage is no longer feasible.
Energy assisted magnetic recording is a recording approach where energy is locally provided to layers of a magnetic recording medium to reduce the coercivity of the recording medium and to temporarily reduce the magnetic field of the medium. These effects allow an applied magnetic writing field to more easily direct (e.g., change, hold) the magnetization of the recording medium. Energy assisted magnetic recording can include heat assisted magnetic recording (HAMR) or microwave assisted magnetic recording (MAMR). HAMR systems typically apply a combination of a magnetic write field gradient and a thermal gradient to the recording medium. MAMR systems typically apply a localized electrical field at a high frequency (e.g., a microwave frequency) to layers of the recording medium. HAMR and MAMR allow for the use of small grain media layers for recording at increased areal densities by increasing the supermagnetic limit. HAMR also allows for larger magnetic anisotropy at room temperature to increase thermal stability, because of the highly stable magnetic materials that are used (e.g., FePt alloys).